The JCMT Gould Belt Survey: first results from the SCUBA-2 observations of the Ophiuchus molecular cloud and a virial analysis of its prestellar core population

Pattle, K. and Ward-Thompson, D. and Kirk, J. M. and White, G. J. and Drabek-Maunder, E. and Buckle, J. and Beaulieu, S. F. and Berry, D. S. and Broekhoven-Fiene, H. and Currie, M. J. and Fich, M. and Hatchell, J. and Kirk, H. and Jenness, T. and Johnstone, D. and Mottram, J. C. and Nutter, D. and Pineda, J. E. and Quinn, C. and Salji, C. and Tisi, S. and Walker-Smith, S. and Francesco, J. Di. and Hogerheijde, M. R. and André, P. h. and Bastien, P. and Bresnahan, D. and Butner, H. and Chen, M. and Chrysostomou, A. and Könyves, Vera (2015) The JCMT Gould Belt Survey: first results from the SCUBA-2 observations of the Ophiuchus molecular cloud and a virial analysis of its prestellar core population. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 450. pp. 1094-1122. ISSN 0035-8711

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Abstract

In this paper we present the first observations of the Ophiuchus molecular cloud per- formed as part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey (GBS) with the SCUBA-2 instrument. We demonstrate methods for combining these data with previous HARP CO, Herschel, and IRAM N2H+ observations in order to accurately quantify the properties of the SCUBA-2 sources in Ophiuchus. We produce a catalogue of all of the sources found by SCUBA-2. We separate these into protostars and starless cores. We list all of the starless cores and perform a full virial analysis, including external pressure. This is the first time that external pressure has been in- cluded in this level of detail. We find that the majority of our cores are either bound or virialised. Gravitational energy and external pressure are on average of a similar order of magnitude, but with some variation from region to region. We find that cores in the Oph A region are gravitationally bound prestellar cores, while cores in the Oph C and E regions are pressure-confined. We determine that N2H+ is a good tracer of the bound material of prestellar cores, although we find some evidence for N2H+ freeze- out at the very highest core densities. We find that non-thermal linewidths decrease substantially between the gas traced by C18O and that traced by N2H+, indicating the dissipation of turbulence at higher densities. We find that the critical Bonnor-Ebert stability criterion is not a good indicator of the boundedness of our cores. We detect the pre-brown dwarf candidate Oph B-11 and find a flux density and mass consistent with previous work. We discuss regional variations in the nature of the cores and find further support for our previous hypothesis of a global evolutionary gradient across the cloud from southwest to northeast, indicating sequential star formation across the region.

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